Flexural Analysis of Prestressed Concrete Monoblock Crossties: Comparison of Current Methodologies and Sensitivity to Support Conditions


Throughout the international railway community, many methods have been developed to analyze the flexural demand of concrete crossties. The investigation described in this paper serves to clarify and improve upon the current language found in the American Railway Engineering and Maintenance-of-Way Association (AREMA) recommended practices for the design of prestressed concrete monoblock crossties. Specifically, this paper will focus on how changes in support condition assumptions affect the flexural analysis of the crosstie. The current flexural analysis methodologies contained in AREMA Chapter 30, EuroNorm (EN) 13230, International Union of Railways (UIC) 713R, and Australian Standard (AS) 1085.14 will be explained and compared. To investigate the theoretical bending moments experienced by the crosstie under varying support conditions, a linear-elastic crosstie analysis model was developed. This model was used to perform a parametric study to determine the sensitivity of the crosstie to changes in ballast reaction along the crosstie. The results of this parametric study were compared to existing design recommendations to find allowable levels of ballast reaction that can occur beneath the crosstie before failure is expected. This model was also used to calculate theoretical bending moment values under ballast reactions measured in the field. Since the theoretical rail seat bending moments exceeded current design recommendations and the crossties did not experience any flexural cracking, it suggests that the tested crossties were either over-designed or behaving as a deep beam. Based on the results of these analyses, recommendations to improve current design and maintenance practices for prestressed concrete crossties will be presented.